Impact of sphincter invasion on T stage definition in rectal cancer

Dear Editor: Uniform stage is the strongest predictor of survival for patients with rectal cancer. Accurate staging is paramount for appropriate patient management and clinical research comparison. Historically, tumor staging is based on local tumor characteristics (T), lymph nodes involvement (N), and presence of distant metastasis (M). In the seventh edition of the American Joint Committee on Cancer (AJCC) staging, T4 was subdivided into T4a (tumor penetrates to the surface of thevisceralperitoneum) andT4b(tumordirectlyinvadesoris adherent to other organs or structures) [1]. These changes were supported by SEER rectal cancer outcomes data that showed a 10 % improvement in 5-year overall survival in patients with T4a lesion compared with T4b [2].